This article was presented as part of Symposium W, "Gallium Nitride and Related Alloys" at the 1999 Fall Meeting of the Materials Research Society held in Boston, Massachusetts, November 28-December 3
We have used time-resolved photoluminescence (PL), with 400 nm (3.1 eV)
excitation, to examine InxGa1-xN/GaN light-emitting diodes (LEDs) before the final
stages of processing at room temperature. We have found dramatic differences in the
time-resolved kinetics between dim, bright and super bright LED devices. The lifetime of
the emission for dim LEDs is quite short, 110 ± 20 ps at photoluminescence (PL)
maximum, and the kinetics are not dependent upon wavelength. This lifetime is short
compared to bright and super bright LEDs, which we have examined under similar
conditions. The kinetics of bright and super bright LEDs are clearly wavelength
dependent, highly non-exponential, and are on the nanosecond time scale (lifetimes are in
order of 1 ns for bright and 10 ns for super bright LED at the PL max). The non-exponential
PL kinetics can be described by a stretched exponential function, indicating
significant disorder in the material. Typical values for 
,the stretching coefficient, are
0.45 -- 0.6 for bright LEDs, at the PL maxima at room temperature. We attribute this
disorder to indium alloy fluctuations.
From analysis of the stretched exponential kinetics we estimate the potential
fluctuations to be approximately 75 meV in the super bright LED. Assuming a hopping
mechanism, the average distance between indium quantum dots in the super bright LED
is estimated to be 20 Å.
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Cite this article as: MRS Internet J. Nitride Semicond. Res. 5S1, W11.58 (2000).
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